为了缓解桥梁梁体在各类因素下的横向偏移或倾覆问题,同时改良现有防偏移设备的刚性阻拦缺陷,以机械设备的减震隔震装置为借鉴,设计了一种基于弹性防偏-塑性卸载理念的梁体横向限位设备.该设备根据折减后的桥墩墩底抗弯强度及梁体横向...为了缓解桥梁梁体在各类因素下的横向偏移或倾覆问题,同时改良现有防偏移设备的刚性阻拦缺陷,以机械设备的减震隔震装置为借鉴,设计了一种基于弹性防偏-塑性卸载理念的梁体横向限位设备.该设备根据折减后的桥墩墩底抗弯强度及梁体横向最大容许位移选择弹簧参数(用于正常情况下的弹性防偏),由折减后的支反力计算薄弱层锚固螺栓的个数(用于大荷载下的卸载保墩).以陕西某曲线连续梁桥为例,以未安装设备桥梁模型为基准,通过有限元分析软件Midas Civil模拟无设备桥梁及有设备后的桥梁在静、动力作用下的位移增量及应力增量.数据对比显示:该设备在限制各静力作用下的径向爬移效果显著(平均位移限制率达70%以上,主要位移诱因的限制率达80%以上);在El Centro Site波大部分时程内,有设备梁体的位移增量和应力增量值较无设备梁体的小,且安装设备后峰值位移(降低率均在90%以上)及峰值应力(平均降低率达50%左右)得到明显降低,这说明该设备可在避免应力集中的情况下,有效减小梁体的动力位移增量,具有良好的抗震/防偏移效果.展开更多
Polyimide(PI)films are widely used in printed circuit boards,electronic packaging,interlayer media,display panels,and other fields.Improving the thermal conductivity of PI film is of great significance to promote effe...Polyimide(PI)films are widely used in printed circuit boards,electronic packaging,interlayer media,display panels,and other fields.Improving the thermal conductivity of PI film is of great significance to promote effective heat removal in microelectronic devices.Herein,melamine cyanurate(MC)with multiple hydrogen bonds was designed and introduced into water-soluble polyamide acid(Ws-PAA)solution via an in-situ co-precipitation method.The MC supramolecule forms a chemical bond at the end of the PI chain,while also confines the adjacent chains through hydrogen bonds andπ-πconjugation,functioning as a tailor to improve the chain arrangement via this molecular welding strategy.The tailored PI/MC films exhibit anisotropic thermal conductivity(TC):the in-plane TC can reach 0.93 W/(mK)while the through-plane TC is 0.60 W/(mK).Micromorphology and structural characterizations confirm the formation of complete heat conduction pathways.The developed films also show potential application prospects functioning as heat dissipation media in microelectronic devices.展开更多
文摘为了缓解桥梁梁体在各类因素下的横向偏移或倾覆问题,同时改良现有防偏移设备的刚性阻拦缺陷,以机械设备的减震隔震装置为借鉴,设计了一种基于弹性防偏-塑性卸载理念的梁体横向限位设备.该设备根据折减后的桥墩墩底抗弯强度及梁体横向最大容许位移选择弹簧参数(用于正常情况下的弹性防偏),由折减后的支反力计算薄弱层锚固螺栓的个数(用于大荷载下的卸载保墩).以陕西某曲线连续梁桥为例,以未安装设备桥梁模型为基准,通过有限元分析软件Midas Civil模拟无设备桥梁及有设备后的桥梁在静、动力作用下的位移增量及应力增量.数据对比显示:该设备在限制各静力作用下的径向爬移效果显著(平均位移限制率达70%以上,主要位移诱因的限制率达80%以上);在El Centro Site波大部分时程内,有设备梁体的位移增量和应力增量值较无设备梁体的小,且安装设备后峰值位移(降低率均在90%以上)及峰值应力(平均降低率达50%左右)得到明显降低,这说明该设备可在避免应力集中的情况下,有效减小梁体的动力位移增量,具有良好的抗震/防偏移效果.
基金funding from the Shanghai Sailing Program (21YF1414200)
文摘Polyimide(PI)films are widely used in printed circuit boards,electronic packaging,interlayer media,display panels,and other fields.Improving the thermal conductivity of PI film is of great significance to promote effective heat removal in microelectronic devices.Herein,melamine cyanurate(MC)with multiple hydrogen bonds was designed and introduced into water-soluble polyamide acid(Ws-PAA)solution via an in-situ co-precipitation method.The MC supramolecule forms a chemical bond at the end of the PI chain,while also confines the adjacent chains through hydrogen bonds andπ-πconjugation,functioning as a tailor to improve the chain arrangement via this molecular welding strategy.The tailored PI/MC films exhibit anisotropic thermal conductivity(TC):the in-plane TC can reach 0.93 W/(mK)while the through-plane TC is 0.60 W/(mK).Micromorphology and structural characterizations confirm the formation of complete heat conduction pathways.The developed films also show potential application prospects functioning as heat dissipation media in microelectronic devices.
